Environment friendly base fluid to replace the toxic mineral oil-based base fluids

ABSTRACT

Embodiments of the invention provide alkyl esters useful as base fluids in oil-based mud compositions, and processes of preparing such alkyl esters. The alkyl esters are produced from raw material waste oil that include vegetable oil. The raw material waste oil can be obtained from the food industry, such as from food chains. The raw material waste oil is purified by removing impurities from it. The raw material waste oil is then esterified with an alcohol in the presence of a catalyst. The resulting alkyl ester products are then separated from triglycerides. The alkyl ester products are then washed and dried.

RELATED APPLICATION

This application is a continuation application of, and therefore claimspriority to, U.S. patent application Ser. No. 12/887,854, filed on Sep.22, 2010, the disclosure of which is incorporated herein by reference inits entirety.

FIELD OF THE INVENTION

The present invention relates to an environmentally-friendly base fluidand methods for producing alkyl esters useful as the base fluid inoil-based mud compositions and related compositions.

BACKGROUND Description of the Related Art

Mineral oil-based base fluids are widely used in oil-based mud (OBM)formulations worldwide. These base fluids have lower fire and flashpoints compared to vegetable and waste vegetable oils, are poorlybiodegradable and could contaminate soil and waterways if serious spillsoccur with drastic reduction in soil fertility and the water quality.Vegetable oils and their derivatives are highly biodegradable, havesuperior environmental characteristics and virtually non-toxic and thusexpected to cause relatively no environmental impact. Besides use inoil-based mud formulations, other types of industries using mineraloil-based fluids to fulfill certain functional tasks also need analternative to mineral oil-based fluids.

Vegetable oils and their derivatives could be a suitable replacement formineral-oils in such applications. Other than highly favorableenvironmental and biodegradation characteristics, vegetable oils andtheir suitable derivatives have high fire and flash points. The highflash and fire points characteristics of vegetable and waste vegetableoils compared to mineral oils ensure better drilling safety inoperation, handling, storage and transportation of vegetable and wastevegetable oil-based base fluids. The excellent fire safetycharacteristics of vegetable oil-based dielectric fluid will make thembetter candidates for high temperature, high pressure (HTHP) drillingoperations.

Mineral oil-based drilling mud spills or discharges, whether accidentalor intentional, can cause serious socio-economic and environmentalproblems as these muds typically have much higher toxicity andsignificantly lower biodegradation characteristics compared to vegetableand waste vegetable oils and their derivatives. It is well known thatthe detrimental effect of mineral oil-based base fluids can cause adrastic change in the health, mobility, mortality rate and life style ofthe population and the habitats of the affected areas, which can lead toa drastic increase in the total operating cost. For these reasons, aneed exists for replacements for the non-environmentally friendlymineral oil-based muds.

Due to the increasing concerns of global and environmental protectionagencies, government and environmental regulatory agents are enactingstringent environmental laws and regulations to minimize problemsassociated with mineral oil-based OBM systems and are imposing stiffpenalties for spills, cuttings disposal, OBM mud discharges whetheraccidental or not. Government agencies in almost every area of the worldare now aware of the potential damage caused by conventional oil-basedmuds and contaminated cuttings. There are now strict rules andlegislations limiting the use of conventional oil-based drilling muds inthe USA, the North Sea, the Adriatic and the CIS. The economic cost ofremediation and reclamation of mineral oil-based mud contaminated lands,cuttings, disposal site is very high. The total loss in revenuesassociated with cuttings and mud transportation and also clean up canexceed thousands of dollars per well with a drastic increase in totaloperating costs. Any unwanted or accidental spills or discharges ofmineral oil-based muds can increase the operating cost further due topenalties and fees to national oil spill recovery and reclamationschemes. The increase in operating cost for losses due to non-productivedrilling time and also cost associated with site restoration can exceedmillions of dollars per annum. The recent realization of the higheconomic impact of mineral oil-based drilling muds due to their shortand long term consequences on the environment, ecosystem, and humanhealth have made operators look for suitable alternatives for oil andgas industry applications. Due to excellent environmental andbiodegradation properties of vegetable, waste vegetable oils and theirderivatives, these oils are potential candidates for the development ofa new generation of OBM systems.

Others have attempted to make products, such as lubricants or biofuels,from vegetable oils. These prior attempts generally did not use recycledwaste vegetable oil. Furthermore, the processes used to produce suchproducts were complicated and required cleaning reagents or absorbingmaterials, such as silicates and clays.

A need exists for a new type of OBM system that is environmentallyfriendly, as well as performs well. Vegetable oils are natural productsand have renewable sources with plenty of supply as per consumer demandand thus the most suitable candidates for substituting petroleum-basedfluids. The advantage of vegetable/plant oils is that they haverenewable sources compared to the limited sources of mineral oils andneed simple and low energy processing and simple equipment for theextraction of the oils. The disadvantage of vegetable oils is that theyhave lower oxidative stability, a higher pour point, and significantlyhigher viscosity compared to mineral oils. Their high viscosity andsusceptibility to oxidation have been the primary obstacles to use themas a base liquid for oil-based mud formulation. The most attractivefeatures of vegetable oil-based fluids are their high biodegradability,very low toxicity, and high fire and flash points to improve operationaland transportation safety. Vegetable and waste vegetable oils areusually 95-100% biodegradable, virtually non-toxic and have no ornegligible impact to the surrounding environment. OBM mud systemsformulated using these vegetable oils or their derivatives pose littleto no danger to aquatic or terrestrial, offshore or onshore, deep wateror shallow water environments.

SUMMARY OF THE INVENTION

In view of the foregoing, embodiments of the present invention arerelated to the development of a readily biodegradable andenvironmentally friendly base oil with viscous characteristics similarto mineral oil-based base fluids used for OBM formulations for oil andgas field applications. Embodiments of the present invention can be usedas replacements for non-environmentally friendly mineral oil-based basefluids with a readily biodegradable vegetable oil-based base fluid tofulfill the increasingly strict environmental laws and regulations ofEPA, state governments, and federal governments.

The methods and compositions of the present invention can also be usedto solve disposal problems associated with large amounts of wastevegetable oils that are produced by the food industry by recycling itfor other industrial uses. Waste and pure vegetable oils and theirderivates have higher fire and flash points compared to mineraloil-based base fluids. Embodiments of the present invention can alsoimprove the operational safety in handling and transportation ofoil-based base fluids and also in HTHP drilling operations. Because ofthe low or negligible dermatological effects of vegetable oils, thewaste vegetable oil-based base fluid can improve the occupational healthand safety of workers at the rig sites using the methods andcompositions of the present invention.

Embodiments of the present invention are not limited to the wastevegetable oil-based base fluid products but also the processes and thetreatment methods used in the development of the product that produced awaste vegetable oil-based base fluid for a new generation of OBMformulations.

More specifically, processes for producing base fluids for use inoil-based mud compositions are provided. As a first embodiment, aprocess for producing alkyl esters useful as a base fluid in oil-basedmud compositions is provided. In this embodiment, a raw material wasteoil comprising fatty acids is esterified with a short chain alcohol inthe presence of a catalyst. The alkyl ester products are then separatedfrom the triglycerides contained in the raw material waste oil. Thealkyl ester products are then washed and dried. To dry the alkyl esterproducts, the alkyl ester products are heated to remove any residualwater or the short chain alcohol.

Another process for producing alkyl esters useful as a base fluid inoil-based mud compositions is provided as an embodiment of the presentinvention. In this embodiment, the process includes the steps ofremoving impurities from a raw material waste oil comprising fattyacids; esterifying the raw material waste oil with a short chain alcoholin the presence of a catalyst; separating alkyl ester products andtriglycerides; washing the alkyl ester products; and then heating thealkyl ester products to remove any residual water or the short chainalcohol.

As another embodiment of the present invention, a process for producingalkyl esters useful as a base fluid in oil-based mud compositions isprovided. In this embodiment, impurities from a raw material waste oilcomprising fatty acids are removed. The raw material waste oil caninclude waste vegetable oil. The raw material waste oil is thenesterified with methanol in the presence of sodium hydroxide. The alkylester products and triglycerides are then separated. The alkyl esterproducts are washed. The alkyl ester products are then heated to removeany residual water or the short chain alcohol.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions. The base fluid includes an alkyl ester including anesterified raw material waste oil comprising fatty acids. The alkylester includes an amount of mono-unsaturated fatty acids greater than anamount of mono-unsaturated fatty acids present in the raw material wasteoil.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the base fluid has a plasticviscosity of less than 6.8 centipoise.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the base fluid has a plasticviscosity ratio of less than 3 centipoise with respect to a Safra oil.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the base fluid has a plasticviscosity ratio of less than 1.5 centipoise with respect to a viscosityof a conventional mineral oil.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the base fluid is morebiodegradable than conventional mineral oil-based base fluids.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the base fluid has higher flash andfire point characteristics as compared to a mineral oil-based basefluid.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the raw material waste oil is abyproduct of a food industry.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the raw material waste oil is wastevegetable oil.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the raw material waste oil has aplastic viscosity of greater than about 50 cP.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the fatty acids includes fatty acidmolecules averaging from 16 carbon atoms to less than 20 carbon atoms.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the raw material waste oil has aplastic viscosity ratio of raw material waste oil to mineral oil that isgreater than about 10 to about 1.

In an embodiment, there is provided a base fluid for use in oil-basedmud compositions of claim 1, wherein the raw material waste oil isbiodegradable.

In another embodiment, a base fluid for use in oil-based mudcompositions is provided. The base fluid includes a primary emulsifier,a secondary emulsifier, a viscosifier, a fluid loss additive, lime, andan alkyl ester including an esterified raw material waste oil comprisingfatty acids. The alkyl ester includes an amount of mono-unsaturatedfatty acids greater than an amount of mono-unsaturated fatty acidspresent in the raw material waste oil.

Various types of raw material waste oil can be used in embodiments ofthe present invention. For example, the raw material waste oil can be abyproduct of the food industry. For example, the raw material waste oilcan be obtained from chain restaurants. As another example, the rawmaterial waste oil can include vegetable oil. The vegetable oil can bewaste vegetable oil that is a byproduct of the food industry. Asindicated previously, the raw material waste oil can include fattyacids. The fatty acid molecules can average from 16 carbon atoms to lessthan 20 carbon atoms. Other suitable types of raw material waste oilwill be apparent to those of skill in the art and are to be consideredwithin the scope of the present invention.

As indicated previously, the raw material waste vegetable oil used inembodiments of the present invention can include a food industry wasteproduct. The food industry waste product typically has differentimpurities arising from different food ingredients and also differentfatty acids, such as saturated fatty acids, mono unsaturated fattyacids, polyunsaturated fatty acids, or combinations thereof. The foodresidues, impurities, and the saturated and the polyunsaturated fattyacids present in the waste cooking oil generally made it unsuitable touse as base fluids in spite of the excellent environmentalcharacteristics of vegetable oil-based fluids. These impurities and thefatty acids made the oil very thick, highly viscous, chemically unstableand thermally degradable and thus were some of the serious drawbacksthat prevented use of the good environmental and biodegradation benefitsof vegetable and waste vegetable oil-based fluids in oil-based mudformulations.

The use of the methods and compositions of the present invention has ledto the development of waste vegetable oil-based base fluid to replacethe relatively toxic and poorly biodegradable mineral oil-based basefluid. Waste cooking oil was selected to eliminate the impact on foodindustry that can arise due to industrial use of a big chunk of purevegetable oil and also to solve the disposal issues associated withwaste vegetable oils by recycling them for other industrial use. Thebase fluid has been developed by removing the all impurities and thenprocessing and treating the filtered oil to produce a low viscous basefluid possessing all the desirable characteristics of a typical mineraloil-based base fluid for formulation of a new generation of oil-basedfluid for oil and gas industry applications. The method embodiments ofthe present invention include the removal of impurities, determinationof the amount of chemicals required for treatment by titration,processing of the oil to remove the triglycerides, washing of the oil toremove excess chemicals, and thermal treatment of the oil to removeexcess water. The treatment and processing techniques used for thisinvention provide a homogeneous, stable, low viscous fluid withdesirable properties that are important for formulation of oil-basedmuds. The base fluid is environmentally friendly and readilybiodegradable and thus expected to have little to no detrimental effecton land, water, surrounding population and the habitats as it is aderivative of vegetable oil-based oils.

The base fluids made in accordance with embodiments of the presentinvention can be used in various applications. The base fluids can beused in drilling muds, fracturing fluids, drill-in fluids, completionfluids, stimulation fluids, or combinations thereof. Other applicationsin which the base fluids of the present invention can be used will beapparent to those of skill in the art and are to be considered withinthe scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features, aspects andadvantages of the invention, as well as others that will becomeapparent, are attained and can be understood in detail, more particulardescription of the invention briefly summarized above can be had byreference to the embodiments thereof that are illustrated in thedrawings that form a part of this specification. It is to be noted,however, that the appended drawings illustrate some embodiments of theinvention and are, therefore, not to be considered limiting of theinvention's scope, for the invention can admit to other equallyeffective embodiments.

FIG. 1 is graph illustrating a comparison of dial readings vs. RPM ofrotational viscometer for different prior art oils (mineral oil (MO),highly refined Saudi Arabian oil (SAO), waste vegetable oil (WVO)) withoils made in accordance with embodiments of the present invention(refined waste vegetable oil (RWVO));

FIG. 2 is a graph illustrating a comparison of PV (plastic viscosity) ofdifferent prior art oils (MO, VO, SAO, VO, WVO) with oils made inaccordance with embodiments of the present invention (RVO, RWVO);

FIG. 3 is a graph illustrating a comparison of PV ratios of differentprior art oils with respect to SAO with oils made in accordance withembodiments of the present invention; and

FIG. 4 is a graph illustrating a comparison of PV ratios of differentprior art oils with respect to mineral oil (MO) with oils made inaccordance with embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Processes for producing base fluid for use in oil-based mud compositionsare provided. As a first embodiment, a process for producing alkylesters useful as a base fluid in oil-based mud compositions is provided.In this embodiment, a raw material waste oil comprising fatty acids isesterified with a short chain alcohol in the presence of a catalyst. Theseparating alkyl ester products are then separated from thetriglycerides contained in the raw material waste oil. The alkyl esterproducts are then washed and dried. To dry the alkyl ester products, thealkyl ester products are heated to remove any residual water or theshort chain alcohol.

In an aspect, the process also includes removing impurities from the rawmaterial waste oil prior to the step of esterifying the raw materialwaste oil. Various methods can be used for removing impurities, such asfood residues, from the raw material waste oil. The resulting base fluidis essentially free from all impurities and food residues that canreduce the functional capability of the fluid. For example, the step ofremoving impurities from the raw material waste oil can includefiltering the raw material waste oil at a pressure in a range of about 5psi to about 10 psi. A low pressure and quick filtration method can beused to remove the impurities and food residues from the raw materialwaste oil. The range of about 5 psi to about 10 psi pressure isgenerally sufficient for quick filtration of the raw material waste oil.Other suitable methods of removing the impurities from the raw materialwaste oil will be apparent to those of skill in the art and are to beconsidered within the scope of the present invention.

Another process for producing alkyl esters useful as a base fluid inoil-based mud compositions is provided as another embodiment of thepresent invention. In this embodiment, the process includes the steps ofremoving impurities from a raw material waste oil comprising fattyacids; esterifying the raw material waste oil with a short chain alcoholin the presence of a catalyst; separating alkyl ester products andtriglycerides; washing the alkyl ester products; and then heating thealkyl ester products to remove any residual water or the short chainalcohol.

As another embodiment of the present invention, a process for producingalkyl esters useful as a base fluid in oil-based mud compositions isprovided. In this embodiment, impurities from a raw material waste oilcomprising tatty acids are removed. The raw material waste oil includeswaste vegetable oil. The raw material waste oil is then esterified withmethanol in the presence of sodium hydroxide. The alkyl ester productsand triglycerides are then separated. The alkyl ester products are thenwashed. The alkyl ester products are then heated to remove any residualwater or the short chain alcohol.

The raw material waste oil can have various properties that make itunsuitable as a base fluid for oil-based mud compositions. For example,the raw material waste oil can have a plastic viscosity of greater thanabout 50 cP. In an aspect, the plastic viscosity can be measured using amulti speed rotational viscometer. As another aspect, the raw materialwaste oil can have a plastic viscosity of about 60.8 cP. As anotherexample, the raw material waste oil can have a plastic viscosity ratioof raw material waste oil to mineral oil that is greater than about 10to about 1. In an aspect, the raw material waste oil can have a plasticviscosity ratio of more than about 20 with respect to the plasticviscosity of a highly refined Safra (Saudi Arabian) oil used fordrilling offshore and sensitive environments. In another aspect, the rawmaterial waste oil used as the raw material has a plastic viscosityratio of about 24.12 with respect to a highly refined Saudi Arabian Oilused for offshore drilling. In another aspect, the raw material wasteoil can have a plastic viscosity ratio of more than about 10 withrespect to the plastic viscosity of conventional mineral oils that areused for OBM formulations. The waste vegetable oil used as the rawmaterial can have a plastic viscosity ratio of about 11.18 with respectto the plastic viscosity of conventional mineral oils used for OBMformulations. In embodiments of the present invention, the PV range ofthe compositions of the present invention is very similar to the PVrange of conventional mineral oils as determined by using a rotationalviscometer.

Both the pure vegetable and the waste vegetable oils could be used asthe raw materials to develop a nontoxic, readily biodegradable andenvironment friendly base fluid. Use of recycled waste vegetable oils ispreferable in embodiments of the present invention. As a benefit ofusing waste vegetable oils, the use of edible vegetable oils forindustrial application can transfer a large amount of pure vegetable oilfrom the food industry, which would reduce environmental issues relatedto disposal of such a large quantity of waste oil.

Various types of raw material waste oil can be used in embodiments ofthe present invention. For example, the raw material waste oil can be abyproduct of the food industry. As another example, the raw materialwaste oil can include vegetable oil. The vegetable oil can be wastevegetable oil that is a byproduct of the food industry. For example, theraw material waste oil can be obtained from chain restaurants. Asindicated previously, the raw material waste oil can include fattyacids. The fatty acid molecules can average from 16 carbon atoms to lessthan 20 carbon atoms. Other suitable types of raw material waste oilwill be apparent to those of skill in the art and are to be consideredwithin the scope of the present invention.

Various types of short chain alcohols can be used in embodiments of thepresent invention. For example, the short chain alcohol can includemethanol, ethanol, propanol, butanol, or combinations thereof. Othersuitable alcohols that can be used in embodiments of the presentinvention will be apparent to those of skill in the art and are to beconsidered within the scope of the present invention.

Various types of catalyst can be used in embodiments of the presentinvention. For example, the catalyst can include sodium hydroxide,potassium hydroxide, sodium alkoxides, potassium alkoxides, orcombinations thereof. Other suitable types of catalyst that can be usedin embodiments of the present invention will be apparent to those ofskill in the art and are to be considered within the scope of thepresent invention.

The invention provides an environmentally friendly low viscous wastevegetable oil-based base fluid for formulation of a new generation ofOBM systems for applications in oil and gas exploration andexploitation. A goal of present invention is to develop a base fluid fora new generation of OBM systems that can eliminate the technicalproblems associated with water-based mud systems and the environmentalproblems associated with mineral oil-based OBM systems.

As indicated previously, embodiments of the present invention include amulti-stage processing and treatment method comprising filtration,treatment, sedimentation and processing of waste vegetable oils that areavailable from the food industry with high impurities and inferiorchemical and physical properties relative to conventional mineraloil-based base fluids. The finished product is a readily biodegradable,environmentally friendly and high fire resistant base oil with viscousproperties similar to mineral oil-based base fluids used for OBMformulations.

The processes used to make the base fluids in accordance withembodiments of the present invention are not complicated and do notrequire additives, reagents, or absorbing materials, as were required inprior art attempts of using vegetable oils to produce various lubricantsor biofuels. Such prior art processes required the use of immersionheaters, pumps, cleaning reagents, negative pressure controllablevessels, and the like. None of these complicated features are requiredin embodiments of the present invention.

Like vegetable oils, waste vegetable oils are mixtures of triglyceridesof fatty acids. The stability of the oil is governed by the fatty acidcontent of the oils significantly. Typical fatty acids of wastevegetable oils can be classified according to their degree ofsaturation/unsaturation into saturated, mono-unsaturated, di-unsaturatedand tri-unsaturated fatty acids. Even though a high level of saturatedfatty acid content will increase chemical stability of an OBM system, itis not desirable above a certain threshold value due to an increase inthe freezing point and viscous characteristics of the base fluid. Highlevels of di-unsaturated and tri-unsaturation fatty acids make the oilvery unstable in air due to oxidation reactions. Elimination of the di-and tri-unsaturated fatty acids so that the amount of such compounds isas low as possible produces base fluids having more desirable physicalproperties. Waste vegetable oils containing high amount ofmono-unsaturated oils are more chemically stable than those having alarge amount of di- and tri-unsaturated fatty acids. Waste vegetableoils containing high amounts of mono-unsaturated oils are useful in OBMformulations. Formulations can also be done using waste vegetable oilshaving lower amounts of mono-unsaturated fatty acids. However, thedegree of difficulty of making the OBM formulation will increase as theamount of mono-unsaturated fatty acids decreases. Hence, the selectionof a waste vegetable oil that has high monounsaturated fatty acidscontent is preferable.

In an embodiment, a base fluid for use in oil-based mud compositions isprovided. The base fluid includes a primary emulsifier, a secondaryemulsifier, a viscosifier, a fluid loss additive, lime, and an alkylester prepared in accordance with the method embodiments describedherein. Other suitable components that can be used in the base fluid inembodiments of the present invention will be apparent to those of skillin the art and are to be considered within the scope of the presentinvention.

The alkyl esters made in accordance with the processes described hereincan be used as a base fluid in oil-based mud compositions. The physicalproperties of the base fluids can vary, depending upon the type of rawmaterial waste oil selected and its fatty acid content, among otherfactors. For example, the plastic viscosity of the base fluid can vary.In an aspect, the base fluid can have a plastic viscosity of about 6.8cp as determined by using a rotational viscometer. As another aspect,the base fluid can have a viscosity ratio of less than about 3 withrespect to a highly refined Safra (Saudi Arabian) oil used in OBMformulation. As an aspect, the base fluid can have a viscosity ratio ofabout 2.73 with respect to the highly refined Saudi Arabian oil used foroffshore drilling.

The properties of the base fluid made in accordance with embodiments ofthe present invention can be compared with conventional base fluids thatcontain mineral oils. For example, the base fluid can have a viscosityratio of less than about 1.5 with respect to the viscosity ofconventional mineral oils that are used in OBM formulations. As anotherexample, the base fluid can have a viscosity ratio of about 1.26 withrespect to the viscosity of conventional mineral oils that are used forOBM formulations.

In an aspect, the base fluid can have a plastic viscosity that iscomparable to the plastic viscosity of any base fluid derived from purevegetable oils. In an aspect, the base fluid is significantly moreenvironmentally friendly than conventional mineral oil-based basefluids.

In an aspect, the base fluid is expected to eliminate the environmentalimpact associated with mineral oil-based base fluids and OBM systems. Inanother aspect, the base fluid is significantly more biodegradable thanconventional mineral oil-based base fluids. In yet another aspect, thebase fluid is readily biodegradable compared to the biodegradationcharacteristics of mineral oil-based base fluids and OBM systems. In anaspect, at least about 80% biodegradation occurs within about 21 days ofexposure of the base fluid in an oxidative environment.

The base fluids made in accordance with embodiments of the presentinvention can be used in various applications. The base fluids can beused in drilling muds, drill-in fluids, completion fluids, stimulationfluids, fracturing fluids, or combinations thereof. Other applicationsin which the base fluids of the present invention can be used will beapparent to those of skill in the art and are to be considered withinthe scope of the present invention.

As an advantage of the present invention, the raw material waste oil isenvironmentally friendly and readily biodegradable. Because the rawmaterial waste oil is biodegradable, the resulting base fluidscontaining the raw material waste oil are much more environmentallyfriendly and readily biodegradable than prior art base fluids thatcontain mineral oils.

As another advantage of the present invention, the based fluids havehigher flash and fire points characteristics to improve operationalsafety while handling, transporting and drilling compared to a mineraloil-based base fluid.

EXAMPLES Impurities and Excess Water Removal

The first step in purifying the waste vegetable oil was the removal ofimpurities such as burnt and unburnt food residues that were present inthe fluid. A low pressure filtration cell with filter paper that haspore sizes less than 5 microns was used for removing the impurities thatare usually larger than 5 microns. A constant pressure of 5-10 psi wasused on the low pressure cell for quick filtration of a significantvolume of waste vegetable oil. Other filtration mediums and adsorbentsthat are capable to remove all impurities and excess water from the oilcan also be used. However, the low pressure filtration method andapparatus were used due to their ease of operation and ability toprocess a significant volume of waste vegetable oil within a shortperiod of time. A multi-cell filtration apparatus was used for removingthe impurities.

Titration to Determine the Amount of Catalyst

The amount of catalyst that was required to process the waste vegetableoil was determined by titration method. The method consisted of mixingof 1 ml of WVO with 10 ml of isopropyl alcohol of 99.2% purity and thenthe addition of 2-3 drops of an indicator fluid (phenolphthalein) intothe mixture to complete the test. The test was done as quickly aspossible because the mixture of WVO and isopropyl alcohol separates incourse of time. The indicator fluid was added drop by drop into theagitated WVO until the color changed to pink. After the end point, themixture was stirred for a while to check the permanency of the pinkcolor.

The titration test was repeated 3 times. All three test results wereused to calculate the average amount of catalyst required to reach theend point. After determining the average value of NaOH based on thetitration test results, a constant value of 3.5 grams was added todetermine the total amount of catalyst required for one liter of WVO(see Table 1). 3.5 gm of NaOH was required as the catalyst for newvegetable oil.

TABLE 1 Showing Amount of catalyst Required for 1 liter of WVO No ofAmount of NaOH Solution Weight of NaOH Titration used for Titration (ml)(gm/liter of WVO) 1 0.72 .72 + 3.5 = 4.22 2 0.7 .70 + 3.5 = 4.20 3 0.68.68 + 3.5 = 4.18

Esterification to Remove Triglycerides

The viscosity of the waste vegetable oil was very high compared tomineral oil but comparable to the viscous characteristics of purevegetable oils. The viscosity of the WVO was reduced significantly tomatch the mineral oil viscosity by esterifying the base oil usingmethanol. The process consisted of determination of the requiredmethanol volume (20% original WVO volume) and the mass of NaOH (4.22 gmNaOH/liter of WVO) needed for esterification of waste vegetable oil.NaOH worked as a catalyst during the processing of the WVO. A highly drycondition was used for acting as an effective catalyst during theesterification process. The methanol should be analytical grade absoluteto improve process efficiency. First the NaOH and methanol were mixedusing a magnetic stirrer and then added to the vegetable oil. The totalmix was then stirred for six hours using a magnetic stirrer to completethe interactions.

Sedimentation

After the catalytic reaction was placed in dynamic condition, the totalreaction product was allowed to stay in static condition overnight tocomplete the sedimentation of glycerol and sludge at the bottom of thecontainer. During the initial settling phase, some emulsion can beformed due to the presence of some emulsion-forming by-products in theester layer. If that happens, the emulsion can be broken by heating theprocessed mass at about 80° C. or adding about 10 ml acetic acid/literof original oil volume to break and prevent the emulsion formation.

Separation and Washing of Esterified Oil

After complete sedimentation, the top clear esterified oil was decantedslowly and washed for several hours using water and stirring with amagnetic stirrer (see FIG. 2). Then, the esterified oil and the washedwater were kept in static condition overnight for effective separationof oil and water phases. The separated oil phase was decanted slowly toremove it from the water phase. The process of washing was repeated twotimes.

Drying of Esterified Oil

At the end of final washing, the washed esterified oil was heated to 80°C. under dynamic condition using a hot plate and a magnetic stirrer toremove water and methanol further from the processed vegetable oil.

Base Fluid

The multi-stage process and treatment methods described herein, such asfiltration, titration, esterification, sedimentation, washing anddrying, reduced the waste vegetable oil viscosity to the level that wascomparable to conventional mineral oil viscosity (see FIGS. 1-4) andthus lead to the development of an environment friendly and readilybiodegradable base fluid in accordance with embodiments of the presentinvention. The newly developed base fluid had a plastic viscosity thatwas marginally higher than the plastic viscosity of conventional mineraloils that were used for OBM formulations. The waste vegetable oil thatwas used as the raw material had a plastic viscosity that was more than11 times higher than the plastic viscosity of conventional mineral oilsthat were used for OBM formulations. A comparative assessment of theviscous characteristics of the newly developed waste vegetable oil-basedbase fluid with respect to a highly refined Saudi Arabian oil, a mineraloil, a vegetable oil and a refined vegetable oil are shown in FIGS. 1-4.All of the data shows a dramatic decrease in the rotational viscometerreadings at different rotational speeds along with a drastic reductionin plastic viscosity and plastic viscosity ratios with respect to theoriginal waste vegetable oil and a pure vegetable oil used forcomparative analyses. The comparison of the plastic viscosity of thenewly developed base fluid with the plastic viscosity of a highlyrefined. Saudi Arabian oil used as a base fluid for OBM formulations foroffshore drilling indicated a plastic viscosity ratio of about 2.5 (seeFIG. 2). The waste vegetable oil that has been used as the raw materialhad a plastic viscosity ratio of more than 24 with respect to theplastic viscosity of the highly refined Saudi Arabian Oil. Therelatively higher plastic viscosity of the new base oil can have apositive impact in OBM formulations as lesser amount of organophilicclays will be required to raise the mud viscosity to the desired level.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereupon without departing from the principle and scope of theinvention. Accordingly, the scope of the present invention should bedetermined by the following claims and their appropriate legalequivalents.

The singular forms “a,” “an,” and “the” include plural referents, unlessthe context clearly dictates otherwise.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

Throughout this application, where patents or publications arereferenced, the disclosures of these references in their entireties areintended to be incorporated by reference into this application, in orderto more fully describe the state of the art to which the inventionpertains, except when these reference contradict the statements madeherein.

What is claimed is:
 1. A base fluid for use in oil-based mudcompositions, the base fluid comprising: an alkyl ester comprising anesterified raw material waste oil comprising fatty acids, wherein thealkyl ester comprises an amount of mono-unsaturated fatty acids greaterthan an amount of mono-unsaturated fatty acids present in the rawmaterial waste oil.
 2. A base fluid for use in oil-based mudcompositions of claim 1, wherein the base fluid comprises a plasticviscosity of less than 6.8 centipoise.
 3. A base fluid for use inoil-based mud compositions of claim 1, wherein the base fluid comprisesa plastic viscosity ratio of less than 3 centipoise with respect to aSafra oil.
 4. A base fluid for use in oil-based mud compositions ofclaim 1, wherein the base fluid comprises a plastic viscosity ratio ofless than 1.5 centipoise with respect to a viscosity of a conventionalmineral oil.
 5. A base fluid for use in oil-based mud compositions ofclaim 1, wherein the base fluid is more biodegradable than conventionalmineral oil-based base fluids.
 6. A base fluid for use in oil-based mudcompositions of claim 1, wherein the base fluid comprises higher flashand fire point characteristics as compared to a mineral oil-based basefluid.
 7. A base fluid for use in oil-based mud compositions of claim 1,wherein the raw material waste oil is a byproduct of a food industry. 8.A base fluid for use in oil-based mud compositions of claim 1, whereinthe raw material waste oil comprises waste vegetable oil.
 9. A basefluid for use in oil-based mud compositions of claim 1, wherein the rawmaterial waste oil comprises a plastic viscosity of greater than about50 cP.
 10. A base fluid for use in oil-based mud compositions of claim1, wherein the fatty acids comprise fatty acid molecules averaging from16 carbon atoms to less than 20 carbon atoms.
 11. A base fluid for usein oil-based mud compositions of claim 1, wherein the raw material wasteoil comprises a plastic viscosity ratio of raw material waste oil tomineral oil that is greater than about 10 to about
 1. 12. A base fluidfor use in oil-based mud compositions of claim 1, wherein the rawmaterial waste oil is biodegradable.
 13. A base fluid for use inoil-based mud compositions, comprising: a primary emulsifier, asecondary emulsifier, a viscosifier, a fluid loss additive, lime, and analkyl ester comprising an esterified raw material waste oil comprisingfatty acids, wherein the alkyl ester comprises an amount ofmono-unsaturated fatty acids greater than an amount of mono-unsaturatedfatty acids present in the raw material waste oil.